Carvings on stone are pretty good persistence-wise, clay tablets have the happy ability to turn into bricks when they've gone through an arson incident. It's the paper, wood, and wax media that were so ephemeral. Two fun sites to see original Latin and Greek epigraphy that has survived:

http://vindolanda.csad.ox.ac.uk/
http://www.csad.ox.ac.uk/POxy/